The wording in the beginning of the containment procedures is a bit vague, in a way that doesn't really add interest to the piece.

with very dilute concentrations

This wording strikes me as odd.

resemble the algae present in so-called "red tides."

1) Why not give the name(s) of the algae? If it's not actually red tide, say what it is.
2) Your " is on the wrong side of that .

greater than encountered in nature

Why not give the actual concentration?

On occasion

I don't really like the use of this. It's very general.

it is an assumption that

I think 'it is assumed' would sound better.

between 5km and 312 meters

I feel like that should be the other way around, and in the same units.

duration and diameter

Diameter of what? I didn't really understand this section.

Why are the instructions on the second person? I feel like they would be in the third person.

Why are the numbers cut from -7 blackboxed?

I like the concept, and the execution isn't bad. The writing is for the most part okay, but there were some issues in regards to tone and flow. As far as the article structure and pacing and such, I feel like it could use some trimming down and simplification. The containment procedures and the beginning of the description kind of dragged on, for me. The way in which things are ordered left me a little confused as to what the SCP was until the very end of the article, which I didn't really like. I feel like the fact that the cloud produces weird stuff should be stressed more.

Thanks for the feedback! I've cleaned up a lot of the tone stuff you mentioned, switched the instructions to be a more detached second person, and clarified the severity enhancement part.

I tried to make the central issue of the SCP clearer: that if a bunch of bad people knew one of the short rituals, they could do it repeatedly and cause a major disaster, there's nothing we can do to stop that, you can refine a ritual to make it shorter, and there may be rituals in the wild we don't know about.

Should I make the possibility of a cascade event even more explicit? I don't want to "show the monster" too clearly.

Because despite the author of the document's confidence that they have all the copies of "101 Games," if you have a copy they missed then knowing which steps to skip drops the duration of that sequence to below roughly 60 seconds, allowing a cascade event. I also intended the implication that whoever wrote "101 Games" knew about the possibility of severity enhancement and deliberately added those steps to prevent it.